Tritium is produced by many different nuclear reactions, mainly those involving neutrons, deuterons and protons. Tritium is also produced by the neutron irradiation of .sup.6 Li in fusion reactor blankets according to the reaction (.sup.6 Li+n .sup.4 He+T). This reaction is also exploited for energy production.
Since tritium, as well as deuterium, is a nuclear fuel, it is recovered and recycled in the fusion reactor. However the presence of impurities, mainly oxides of tritium and to a lesser extent, oxides of deuterium, formed as a results of the interaction of tritium with the internal surfaces of the system, is extremely detrimental for the re-use of the gas as a fuel in nuclear fusion. This requires purification of the impure tritium.
The oxides of tritium include T.sub.2 O (tritiated water) and mixed compound such as TDO and THO. The oxides of deuterium include D.sub.2 O (heavy water) and mixed oxides such a DTO and DHO.
Conventional techniques use physical adsorbents, such as molecular sieves, or zeolites, kept at cryogenic temperatures to condense these compounds. These oxides are then disposed of as nuclear waste or are treated by electrolytic processes or by thermal dissociation on iron grids at high temperature to recover tritium.
All these prior processes pose serious environmental problems due to the radioactivity of tritium and its compounds. Liquid T.sub.2 O is particularly dangerous because the radioactivity is more concentrated in the liquid form than is the vapour form.
Intermetallic compounds of the type ZrM.sub.2 are known in the literature. Specific articles on this subject can be found for example in the Journal of the Less-Common Metals, Vol. 53 (1977) p. 117-131 by D. Shaltiel, I. Jacobs and D. Davidov, Vol. 130 (1987) p. 25-31 by H. Fujii, M. Saga and T. Okamoto, as well as the Journal of Nuclear Materials, Vol. 170 (1990), p. 217-231 by R-D. Penshorn, M. Devillers and M. Sirch. See also U.S. Pat. No. 4,586,561 regarding these intermetallic compounds.
All the above literature refers to the good sorption characteristics for hydrogen of these compounds (and therefore of its isotopes).